1. Field of the Invention
The present invention relates to a control device for a mobile robot and particularly, to a control device for a mobile robot which allows the robot to run through a narrow passage and/or between obstacles with a minimum of hunting and zigzag motion and a less number of turns and to escape from its deadlock state where the robot is stalled in a limited location such as a corner in a target area for the robot to run throughout.
2. Description of the Related Art
Mobile robots including a cleaner robot, a mower robot, a plasterer robot, and an agricultural sprayer robot are known which automatically run throughout a given area for accomplishment of its imposed task. For example, a cleaner robot is disclosed in Japanese Patent Laid-open Publication No. HEI 5-46246 which first runs about in a target room to be cleaned to map out a running or cleaning area through detection of the size and shape of the target room and the locations of obstacles in the room. Coordinates data produced by the mapping are then used for a mobile robot to clean the room while running in a zigzag pattern or a spiral pattern in which the radius of circling is gradually decreased in every turn. The robot includes contact sensors and supersonic sensors for detecting walls around it to determine its route and a distance meter for measuring the traveled distance to know the end of a circling motion. Also, another mobile robot for running around throughout the whole area of a given floor is disclosed in Japanese Patent Laid-open Publication No. HEI 5-257533.
Such conventional mobile robots are generally provided with a number of sensors of which outputs are used for acquiring the data of an area to be traveled and determining the operations to be performed for running through. More particularly, the outputs of the sensors are constantly transferred to a central controlling unit which in turn determines the controlling action for steering the robot at high accuracy on the basis of the sensor outputs. Driving actuators such as motors are controlled based on said determinations.
When the central controlling unit handles the outputs of all the sensors, its system should be sophisticated and its processing speed will be lowered. Such a lower processing speed may retard to take an averting action when encountering an obstacle such as a wall. Also, required are time for mapping, teaching, and settings of relevant thresholds and initial values for various kinds of controls, and skills for the settings.
Accordingly, the conventional mobile robots are so bulky in size and heavy in weight and costly that their applications will be limited. For example, the limited applications are known as transporting robots and cleaning robots in plants.
Not all robots have to run throughout the entirety of a target area at a higher accuracy but some robots are allowable to run throughout the area at a considerable degree of accuracy. Their routes and directions may not be critical. In some cases of a cleaning robot, for example, the area to be cleaned has not always to be covered in its entirety but some of the area can be remained uncleaned. Depending on their requirements, some mower robots must produce highly neat traces of mowed area and the others are expected to perform a mowing operation only at a substantial level.